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Date: Mon, 2 Jan 2012 19:09:18 -0700
From: Stephen John Smoogen <>
Subject: Re: Testing longer than 16 character words in crypt-md5

On 2 January 2012 19:00, Solar Designer <> wrote:
> On Mon, Jan 02, 2012 at 06:50:42PM -0700, Stephen John Smoogen wrote:
>> I see that the MD5-crypt ($1$) implementation in john the ripper maxes
>> out at 15 characters, but other versions such as what I could figure
>> out in glibc do not limit to that amount. My initial guess is that the
>> limitation is due to some sort of speed up used in hashing.
> Yes, that's the case.
>> My want is to check to see how many passwords are using an email
>> address with some minimal changes that John the Rippers rules are
>> great for. but most of the accounts are over 16 characters in length.
>> Currently I am looking at using JTR to output the modified and then
>> doing an awk script to feed that to openssl but that seems slower and
>> missing some obvious herpderp item I am not seeing.
> You can simply use --format=crypt to make JtR use the system-provided
> code.  Of course, this will be a lot slower than JtR's optimized code.
> I suggest that you do this in an OpenMP-enabled build.

Thankyou for the quick answer on this. When I read the documents I
somehow kept thinking --format=crypt would be the standard Unix DES
version which made me not look at it any further. An OpenMP version
will be what I will need to look at long term.. for a test case it is
a 1 CPU E5300 until I can get a better cluster.

> Alexander

Stephen J Smoogen.
"The core skill of innovators is error recovery, not failure avoidance."
Randy Nelson, President of Pixar University.
"Years ago my mother used to say to me,... Elwood, you must be oh
so smart or oh so pleasant. Well, for years I was smart. I
recommend pleasant. You may quote me."  —James Stewart as Elwood P. Dowd

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